The present invention relates to a power assist anti-tip wheel system for invalid carriage, and more particularly to an anti-tip wheel system equipped with assistant power source to assist an invalid carriage in travelling on a rough road. The upgrade of our living quality and medical level allows us to help more invalid people who are otherwise ignored by the general public. Meanwhile, there are better welfare policies and systems developed in nowaday society, including the provision of various types of traffic means suitable for invalids to assist in their movement. For those invalids who can not walk, there were manually-operated wheelchairs available to assist them to move around. However, such manually-operated wheelchairs can be used only by those invalids whose hands and upper half trunk are in good condition. To meet the needs of invalids whose hands and upper half trunk are not in good condition, there is now electric wheelchair developed and available in the market. The introduction of electric wheelchair to the market is really a good news to the invalids who can not move their hands and legs easily. Since the electric wheelchair has timely solved the pressing need of invalids in traffic even though there are still high risks of accidents on road, the quantity of such electric wheelchair increases from day to day.
On the other hand, motorized vehicles, particularly the automobile and motorcycle, have become a necessary traffic means in our daily life. A problem with automobiles and motorcycles is their exhaust which seriously pollute the air. Under the inevitable trends of environmental protection, environmental friendly electric vehicles are developed and produced. Among these electric vehicles, there is a motorized invalid wheeled vehicle which is light in weight and easy to operate and is therefore widely welcome by many young students, housewives, invalids, and the aged. Such motorized invalid wheeled vehicle has gradually become a main traffic means of invalids for use within short distance.
FIGS. 1 and 2 illustrate two examples of the conventional motorized invalid wheeled vehicles for use by the aged and invalids. The transmission of such wheeled vehicles for use by the aged and invalids. The transmission of such motorized invalid wheeled vehicles can be generally divided into three types according to the designed center of gravity of the wheels, namely, the front-wheel drive, the rear-wheel drive, and the middle-wheel drive. In either drive type, it is necessary to mount at least one anti-tip wheel on the vehicle to prevent the vehicle body from tipping over forward or backward and thereby dangering the aged or invalid operating the vehicle. The motorized invalid wheeled vehicle shown in FIG. 1 is of the type of front-wheel drive with a center of gravity located at a front portion of the vehicle. And, the vehicle shown in FIG. 2 is of the type of rear-wheel drive with a center of gravity located at a rear portion of the vehicle. In either case, the motorized invalid wheeled vehicle is driven by a pair of drive wheels C provided between pilot wheels A and at least one assist anti-tip wheel B. The drive wheels C are actuated by an electric motor D to cause the invalid wheeled vehicle to move forward or backward and/or to turn rightward or leftward.
The at least one anti-tip wheel B is used to protect the short vehicle body from dangerously tipping over forward or backward during moving upward or downward on a slope or due to improper operation of the vehicle. As a result, the provision of the anti-tip wheels B have become a very important part of the motorized invalid wheeled vehicle. Generally, the anti-tip wheel B is located at a position slightly higher than a plane in which the drive wheels C and the pilot wheels A locate. The anti-tip wheel B must be adequately located at a proper height, lest it should become meaningless. An overhigh anti-tip wheel B shall fail to protect the vehicle from tipping over, and an overlow anti-tip wheel B shall always contact with the road surface and makes the operator uncomfortable during driving.
Moreover, in consideration of an active operation of the conventional motorized invalid wheeled vehicle, the pilot wheels A and the at least one assist anti-tip wheel B are so designed that they have diameters smaller than that of the drive wheels C. And, due to limitations in the transmission of power, the drive wheels C can not have a too big diameter as that of the general wheelchairs. As a result, the electric wheelchairs illustrated in FIGS. 1 and 2 can not be conveniently operated when they are used to travel on a rough road. FIGS. 3, 4 and 5 respectively illustrate the rear-wheel drive motorized invalid wheeled vehicle as shown in FIG. 2 travelling on an ascending slope, over a recess, and across a bulge. As shown in the figures, the drive wheels C tend to become suspended when the vehicle passes the slope, the recess or the bulge because there is a difference in height existed between such irregularities and the road surface, as well as because the drive wheels C, the pilot wheels A, and the at least one anti-tip wheel B are not on the same plane. When the drive wheels C become suspended without touching the road or ground surface, they shall fail to supply power to the vehicle for the same to move. That is, the drive wheels C shall idle and cause the whole vehicle to slide downward, be stuck in the recess, or be stopped at the bulge. These conditions surely will cause inconvenience and considerable dangerous conditions may also occur on the front-wheel drive motorized invalid wheeled vehicle illustrated in FIG. 1. Therefore, it is desirable to develop an improved motorized invalid wheeled vehicle to solve the above mentioned problems.